This is veerrry blurry.
Looks like some type, the yellow shape is the same type with "Offset path". Then some shadow colored in black and some other shadow colored in white. But maybe different when viewed as a sharp version.
Type in your word (LET)
Convert it to outlines
Object - offset path (rounded) for the yellow one
Then select the white LET and go to Effects - Stylize - Drop Shadow and play with that.
Nothing 3D here
As I can see
the offset is curve out and close the text in the part that shadow isn't drop
or is just a shadow but make a illusion that the offset curve out
How can I do this?
Sorry for Bad English
You can keep your text live--no need to convert it to outlines.
Look at the screen shots below. In each one I have one of the LET words selected in the layers panel (on the left side of the text).
The text used here is Franklin Gothic Heavy Italic. You can use any font you desire, but you likely will have to kern a different amount than I did. Both pieces of text are kerned to -20 in this example
First the gold-colored lettering. Use the Appearance Panel to add the offset path. It will make it easier to change for your font.
And next the white-colored text that has the drop shadow added, also via the Appearance Panel.
Take care, Mike
Seemingly, the dark shadowy parts do not follow any 3D or other general shaping; rather they seem to be (reverse) highlights of specific parts of the outer shapes of the letters.
You can recreate them by creating paths with drop shadows of the desired shapes and depths, then hide the paths beneath the letter shapes but above the yellow path in the stacking order so that (only) the desired portions of the drop shadows show.
Sorry for old English.
I typed LET, that's all.
Seriously, what is the practical purpose about posting an image remarking that this is something you didn't create using AI ?
I could appreciate it if you were providing some hints about what you did and about what programme you were talking about here.
But you did not. Looks like it's merely a showcase …